import numpy as np
import cv2
from matplotlib import pyplot as plt

img = cv2.imread('pic2.jpg')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
corners = cv2.goodFeaturesToTrack(gray, 25, 0.01, 10)
# 返回的结果是  [[ 311.,  250.]] 两层括号的数组。
corners = np.int0(corners)
for i in corners:
    x, y = i.ravel()
    cv2.circle(img, (x, y), 3, 255, -1)
plt.imshow(img), plt.show()